| Conflict: | Achaemenid Civil War (522-520 BC) |
| Date: | 522 BCE – 520 BCE |
| Result: | Victory for Darius |
| Place: | Achaemenid Empire |
| Combatant1: | Achaemenid Empire (Darius' faction) |
| Combatant2: | Achaemenid Empire (Bardiya or Gaumata) |
| Strength1: | Unknown |
| Strength2: | Unknown |
| Casualties1: | Unknown |
| Casualties2: | Unknown |
| Commander1: | Darius the Great Hystaspes Intaphrenes Otanes Gobryas Hydarnes Megabyzus Aspathines Dadarsi Vahumisa Takhmaspada Artavardiya Vivana |
| Commander2: | Bardiya or Gaumata Patizeithes Nebuchadnezzar III Açina Martiya Phraortes Tritantaechmes Frada Vahyazdata Arakha Atamaita |
Between 522 and 520 BCE, a large scale civil war broke out within the Achaemenid Empire over the mysterious circumstances surrounding the death of Achaemenid King of Kings Bardiya and the ascension to the throne of Darius the Great.